1. Field of the Invention
The present invention relates to an image forming apparatus such as a copier, a printer, a facsimile machine, or a multi-function apparatus having one or more capabilities of the above devices.
2. Description of the Related Art
In an image forming apparatus employing electrophotography, friction between a developer control member and a developer, friction between a developer carrier surface and the developer, and friction between developer particles cause heat to be generated and the heat generated increases a temperature of the developer. In addition, heat around the driving units such as gears, shafts, and bearings of a developing roller and a developer agitating screw is transmitted, via a screw shaft or a case that supports the shaft and the bearing, to increase the temperature of the developer. The increase in the temperature of the developer causes such problems as agglomeration and degradation of the developer.
To solve the above-described problem, it is possible to cool the developer. For example, JP-2009-009074-A discloses a method to cool the developer by blowing air onto the developer from the side of the developer unit.
Similarly, JP-2008-250284-A provides a duct in the image forming unit to block heat from a fixing unit and cool the image forming unit.
Further, JP-2009-288583-A discloses another approach, in which a duct is defined by a guide rail used for attaching a developer unit to a developer case, through which air is blown, thereby cooling the developer.
The above approaches are used to cool the developer via the developer case. By contrast, JP-2006-145727-A discloses a method of blowing air onto front and rear shaft bearings of the developing roller to counter the temperature rise of the developer due to the heat generated at a driving part.
However, none of the above cooling means and methods cools both the developer case and the driving part. If used in combination the cooling units would need to be provided at two locations in the front and the back sides of the developing device, which inevitably increases the size of the apparatus and its cost.
Further, it is known that energy lost as heat from the motor itself as the power source and the heat transmitted via the gears is propagated via the apparatus main frame and the internal air to the developer.